一氧化碳分子在Pt/t-ZrO2(101)表面的吸附性质

运用广义梯度密度泛函理论(GGA-PW91)结合周期平板模型方法,研究了CO分子在完整与Pt负载的四方ZrO2(101)表面的吸附行为.结果表明:表面第二层第二氧位和表面第二桥位分别为CO分子和Pt原子在完整ZrO2(101)表面的稳定吸附位,且覆盖度为0.25ML(monolayer)时均为稳定吸附构型,吸附能分别为56.2和352.7kJ·mol-1.CO分子在负载表面的稳定吸附模式为C-end吸附,吸附能为323.8kJ·mol-1.考察了CO分子在负载表面吸附前后的振动频率、态密度和轨道电荷布居分析,并与CO分子和Pt原子在ZrO2表面的结果进行比较.结果表明,C端吸附CO分子键长为0.1161nm,与自由的和吸附在ZrO2表面后的CO相应值(0.1141和0.1136nm)相比伸长.吸附后C―O键伸缩振动频率为2018cm-1,与自由CO分子相比发生红移;吸附后CO带部分正电荷,电子转移以Pt5dCO2π的π反馈机理占主导地位.

Adsorption Properties of CO Molecules on Pt/t-ZrO2(101) Surfaces

We studied the adsorption of CO molecules on perfect and Pt-adsorbed t-ZrO₂(101) surfaces using a periodic slab model by PW91 of generalized gradient approximation (GGA) within the framework of density functional theory. The results indicated that the second sub-surface oxygen and the second bridge sites are the most stable adsorbed sites for CO and Pt on the ZrO₂(101) surface, respectively. When the coverage is 0.25 ML (monolayer) the most stable models were obtained with adsorption energies of 56.2 and 352.7 kJ·mol^-1. The most stable model of CO adsorbed on the Pt/t-ZrO₂(101) surface was obtained by C-end adsorption with an adsorption energy of 323.8 kJ·mol^-1. We considered vibrational frequency calculations, density of states and the Mulliken population of the adsorption systems before and after adsorption and these were compared for CO and Pt adsorption onto the ZrO₂ surface. The results indicate that the C―O bond length of 0.1161 nm after adsorption at the C-end is elongated compared with the 0.1141 and 0.1136 nm of free and adsorbed on ZrO₂. The vibrational frequency of CO at 2018 cm^-1 is red-shifted compared with free CO. CO has some positive charge after adsorption and charge transfer is predominantly by the π back-donation bonding mechanism of the Pt 5d→CO 2π orbital.